800 A service

[infinity]

He is asking for two sets of 500
Wanted to see if going aluminum we’ll be better price

Post #13 has the alternate for aluminum. I would use aluminum if the engineer allows it and the equipment can handle it.

 

[electrofelon]

He is asking for two sets of 500
Wanted to see if going aluminum we’ll be better price

Aluminum has gone up quite a bit, but I recently checked (about 3 weeks ago) and copper was about 50% more for 200 A -ish condictors.

As others have said, you might have to get approval for changing what is on the plans depending on a variety of factors, but I'm sure you know that.

 

[Sparky9527]

I get 4 sets of 300 kcmil Al in two raceways for the full 800 amps. 260*2*80%*2=832 amps. Raceway fill isn't an issue.

I am a little confused here. So we have 4 set of 300 Kcmil AL conductor in two raceways, and this give you 832 Amp. I believe we are using 90 degree column from 310.15 b16 table.

Your choices are 4 parallel sets of 300 kcm with 2 sets in each conduit which will give you a total of 736 amps. So if the calculated load is 736 or less you could connect to an 800 amp breaker.
For a full 800 amp service you need 4 parallel runs (2 in each conduit) of 350 kcm

But from this calculation, I believe this is using 75 degree column. So my question is should we using 90 degree column, or 75 degree column in this case? Any advise would be greatly appreciated.

 

[Dennis Alwon]

I am a little confused here. So we have 4 set of 300 Kcmil AL conductor in two raceways, and this give you 832 Amp. I believe we are using 90 degree column from 310.15 b16 table.

But from this calculation, I believe this is using 75 degree column. So my question is should we using 90 degree column, or 75 degree column in this case? Any advise would be greatly appreciated.

For de-rating you can use the 90C as long as the insulation on the conductor is rated 90C. The final overcurrent protective device cannot be larger than the 75C rating. 300kcm at 90C ends up at 832 amps. This is fine for an 800 overcurrent protective device.

300kcm @75 C is 230 amps -- 230 x 4 = 920 amps so clearly the 75C column is higher than the overcurrent protective device rating.

 

[Sparky9527]

For de-rating you can use the 90C as long as the insulation on the conductor is rated 90C. The final overcurrent protective device cannot be larger than the 75C rating. 300kcm at 90C ends up at 832 amps. This is fine for an 800 overcurrent protective device.

300kcm @75 C is 230 amps -- 230 x 4 = 920 amps so clearly the 75C column is higher than the overcurrent protective device rating.

Great. I think I got it. Thanks.